Dimerization of butadiene



Patented Apr. 26, 1949 2,468,432 DIIVIERIZATION OF BUTADIENE Herbert L.Johnson, Media, Pa., assignor to Sun Oil Company, Philadelphia, Pa., acorporation of New Jersey No Drawing. Application February 12, 1946,Serial No. 647,210

8 Claims.

This invention relates to the polymerization of butadiene and certain ofits derivatives employing for this purpose a contact mass consistingessentially of silicon carbide to obtain materially higher yields ofproducts, particularly dimer products, than have been obtainedheretofore with other contact masses. More particularly, the inventionrelates to the treatment at an elevated temperature of butadiene,butadiene having one or two methyl groups, or mixtures of thesecompounds, in the presence of a contact mass con sisting essentially ofsilicon carbide to obtain materially higher yields of polymerizationproducts, particularly dimer products, than have been heretoforeobtained with other contact masses. A particularly important advantageand characteristic feature of the invention resides in the fact thatwith the use of silicon carbide as contact mass the course of thepolymerization reaction can be directed, under certain hereinafterspecified conditions, to yield predominantly the dimer products to thesubstantial exclusion of materials boiling either higher or lower thansaid product and in some instances to form no material boiling at alower temperature than the dimer product.

Contact masses which have been employed heretofore to polymerizebutadiene and its homologues have been found to give yields of polymerproducts which are substantially lower than those which can be obtainedemploying silicon carbide according to this invention. Furthermore, thecontact masses heretofore employed have been found not to exhibit thedirective influence or effect obtained with silicon carbide, asdescribed above, namely that substantially all the product formedconsists of the dimer product and especially that it is possible toobtain the dimer product, under certain conditions, to the absoluteexclusion of the formation of materials boiling lower than the boilingtemperature of the dimer product.

Thus, according to the invention, there is provided a novel process forthe treatment of a butadiene compound in the vapor phase at an elevatedtemperature with a contact mass consisting essentially of siliconcarbide to obtain yields of polymerization products which aresubstantially higher than any yields heretofore obtained, as well as aprocess for the treatment of a butadiene compound at an elevatedtemperature and certain other conditions, hereinafter disclosed, toobtain high yields of substantially the dimer product and in some cases,under still more specific conditions, to obtain the dimer 2 product tothe absolute exclusion of any materials boiling lower than the boilingtemperature of the dimer product and to the substantial exclusion ofmaterials boiling higher than the dimer product. Herein and in theclaims the term butadiene compound includes only butadiene, butadienehaving one or two methyl groups, or mixtures thereof. Since theinvention is pre-eminently suited to the treatment of butadiene it willnow be more fully described with reference thereto, particularly withrespect to its polymerization or dimerization to vinylcyclohexene.

The temperature at which the contact mass is employed can be variedconsiderably. However, for the polymerization, generally, a temperaturewithin the range 375 C5450 C. will be employed. For the dimerization thetemperature will be within the range 385 C.-435 C., and will bepreferably about 425 C.

The pressure at which the polymerization or dimerization reaction iseffected is important. For the polymerization reaction, generally, apressure within the range atmospheric to about 200 lbs/sq. in. gaugewill be employed. For the dimerization reaction a pressure within therange 15 -1bs./sq.in.-'75 lbs/sq. in. will be employed and will bepreferably about 35 lbs/sq. in.

Generally a rate within the range 2-8 grams/ minute/200 grams of contactmass will be employed for the polymerization reaction. For thedimerization reaction a rate within the range 3-6 grams/minute/200 gramscontact mass will be employed and the rate will be preferably within therange from about 4 to about 5 grams/minute/200 grams contact mass.

As stated, a characteristic feature of the invention is that it ispossible under the herein disclosed conditions to substantially dimerizethe charging material, that is, it is possible to polymerize to thedimer product with little or no formation of lower boiling materials orsubstantial formation of higher boiling materials. As a result of thischaracteristic of the invention high yields of products, particularly,the dimer products, can be obtained and on recycling any unconvertedcharging material these already high yields can be substantiallyincreased since loss through undesirable materials boilin lower andhigher than the desired products is greatly minimized.

As stated, the contact mass employed according to the invention isessentially silicon carbide. A silicon carbide which has been foundsuited to the practice of the invention is sold in the trade by TheCarborundum Company. Obviously contact mass is preferably in asub-divided state. Particles having a cylindrical shape and measuring 1%inch in diameter as well as length have '4 diene having one methylsubstituent group and butadiene having two methyl substituent groupswhich comprises contacting such compound in the vapor phase at atemperature within the been employed. Other sizes can be employed, rangeof 375-450 C. with a contact mass conthe essential condition being goodcontact besisting essentially of silicon carbide.

tween the butadiene compound and the contact 2. Method according toclaim 1 wherein the mass. Also, the contact mass should not causebutadiene compound is butadiene.

too grea a pre r p hrough the conversion 3. Method according to claim 1wherein the tube for practical operation reasons. butadiene compound isa methyl butadiene.

In use, some coke or heavier polymer mate- 4. Method according to claim1 wherein the rials will eventually accumulate upon the contactbutadiene compound is a dimethyl butadiene. mass. This can easily beburned off employing 5. Method according to claim 1 wherein the methodswell known in the art and the masscan pressure is within the range ofatmospheric to be used almost indefinitely. The character of 200lbs./sq.,in. silicon carbide will at once cause an appreciation 6.Method according to claim 1 wherein the of its pre-eminent suitabilityas a contact mass 'butadiene compound is charged at a rate of 28 forextended use periods. grams/minute/200 grams of contact mass.

The followin table illustrates results obtained: 7. Method of dimerizingbutadiene which com- Oonditions Yields, Per Cent Contact Rate gmsJ MassPress B0lll.l 1g Vmyl Boiling 7 -ecycle;

Tit?" itt-e l-ti liiiiiiid than: his; tense: taiiae i 425 so 3. 9 51. a0.6 31. 1 12. 4 i 64. 0. 9s. 2 425 -60 4.1 49.9 38.7 8.7: 77.31 97.3 42590 7.8 27.9 14.7 17.4 34.3 ,zas -94.0 425 a s. s 85.9 12. a 1.8 87. 4100 400' 60 4.2 72.1 18.1: 5.0 455.0 95.3 400 90 c. 5 49. a 12. 2 l6. 217. 1 32.3 9,5..4

It is to be noted that, owing to a characteristic prises contactingbutadiene in the vapor phase feature of the invention, namely thatundesired at a temperature within the range of 375-450 C. products canbe avoided, the recycle yields are and a pressure within the range ofatmospheric high, to about 200 lbs/sq. in. with a contact mass con- Itwill be obvious to those skilled in the poly- Sis e sentially o 51 00.1C emerization art that modification and variation 8. Method according toclaim 7 "wherein the are possible within the scope of the inventiontemperatu is within ge Of 8 -435" -C., the essence of which is that abutadiene comthe pressure is wi nth ran of s./ qpound specificallybutadiene can be polymerized, d' \butadiene is charged 917a rate ofspecifically dimerized, under the aforesaid conin grams n act ass.ditions employing a contact mass consisting es- HERBERT JOHNSON-sentially of silicon carbide, in yields exceeding by p 4 such an amountthe yields heretofore obtainable REFERENCES CITED with other contactmasses, and in certain cir- The following references .are of record inthe cumstances without the formation of materials file of this patent:boiling at a temperature lower than the boiling temperature of the dimerproduct, as to amount UNITED STATES PATENTS to unpredictable results.Number Name Date I claim: 2,383,189 Hancock Aug. 21, 1945 1. Method ofdimerizing a :butadiene com- 2,39 49 Doumaniet a]. Feb.,12, 1946 poundof the group consisting of butadiene, buta- 2,40 ,414 Doumani et al June4, 194

